Why Central New York is a hot bed for Eastern equine encephalitis

David Lassman / The Post-Standard, 2004A plane sprays for mosquitoes in 2004 as it flies over the Cicero Swamp. Oswego County has decided to undertake aerial spraying to combat Eastern equine encephalitis.

Oswego County, NY -- Only five people in New York state — the latest a 4-year-old Oswego County girl — have died of Eastern equine encephalitis in the last 40 years.

All five lived in Central New York.

Why are we so hard hit by EEE? A State University College of Environmental Science and Forestry expert says what’s relatively unique about this area is the number of swamps with hardwood trees. This type of swamp is the prime breeding ground and living area for the mosquitoes who carry EEE.

Lawrence Abrahamson, senior research associate emeritus, said the area from Oneida Lake west to Lake Ontario is swampy land filled with hardwood trees.

“It’s ideal for the buildup of these mosquitoes,” he said. “The swamps don’t have free flowing water like in the south or other areas of New York.”

EEE is extremely rare. On average there are six cases a year among humans, and most are in Massachusetts, Florida, Georgia and New Jersey, said Dr. Roy Gulick, the chief of the Division of Infectious Diseases at Weill Cornell/New York Presbyterian Hospital.

Onondaga, Oneida, Madison and Oswego counties are the most at risk of EEE cases, which are fatal in about one-third of victims, according to the state Health Department. Since 1970, five people have died of the virus — Maggie Wilcox, 4, of New Haven last Sunday; an Onondaga County man last year; an Oswego County resident in 2009; a 7-year-old Camillus boy in 1983 and an Oswego County child in 1971.

Abrahamson, who has studied insects and pesticides for his entire career, said the EEE virus thrives and is spread by birds and mosquitoes. Horses do not spread the disease, he said.

He believes the disease got its name because when it was first discovered, it was a virus that primarily killed horses.

“The virus is maintained in the environment between mosquitoes and birds,” he said. “People and horses are dead-end hosts. When people and horses are bitten by the mosquitoes and get EEE, they do not transmit it to any thing else.”

Abrahamson said this is how the virus is transmitted:

Ö¤A bird has the disease. Birds do not die from EEE.

Ö¤One particular type of mosquito that feeds 98 percent of the time on birds bites the infected bird. It picks up EEE. Those mosquitoes also can bite other non-infected birds, thus transmitting the disease to those birds.

Ö¤These mosquitoes rarely if ever bite humans. But they keep the virus alive and well by continually picking up the disease from infected birds and spreading it to other birds.

Ö¤Mosquitoes that do bite humans also will bite birds. So they pick up EEE by biting the infected birds. Then if they bite a human, the human can have the EEE virus deposited in his or her blood system.

“If the birds died of EEE, we wouldn’t have a problem,” Abrahamson said. “The virus would die out.”

There have been 16 pools of mosquitoes infected with EEE found in Oswego County in the last couple of weeks. Two horses and a dog have died of the virus. A horse in Oneida County also died of EEE.

Both Abrahamson and Dr. Dennis Norfleet, Oswego County’s director of public health, said most people bitten by an infected mosquito show no signs of illness. A few will feel sick for a couple of days, like they have the flu.

But in a rare few, the virus will erupt into encephalitis — inflammation of the brain. By the time the virus reaches this point, it is too late for doctors to do much. People who don’t die are often left with brain damage.

Symptoms are extreme headache, fever, irritability, restlessness, drowsiness, anorexia, vomiting, diarrhea, cyanosis, convulsions and coma, according to the Centers for Disease Control website. A third of people diagnosed with EEE will die. There is no treatment for the virus.

Abrahamson said believes the extremely wet spring resulted in the explosion of EEE in Oswego County. Spraying is the only way to combat the spread of the disease. He said some experts have voiced the idea of killing the mosquito larvae in the spring, but he said “this would cost millions of dollars. You couldn‘t do it.”

The pesticide normally used in spraying is sumithrin, with the brand name Anvil. Oswego County announced Friday it would be using permithrin, with the brand name Kontrol 30-30.

Abrahamson said Anvil and Kontrol 30-30 work pretty much the same with the same results. Anyone who wants to read more about Kontrol 30-30 should go to this website.

“You spray where the adults are flying,” he said. “About one-half ounce of active ingredient per acre is used.”

He said municipalities that spray take special precautions, telling people to close windows when spraying is going on and to bring pets indoors. Oswego County’s news release about spraying said it wouldn’t be done over organic farms or near bee colonies.

Abrahamson said while the insecticide is strong enough to kill the mosquitoes, it would not kill a person or animal if inhaled. It could be a problem for people with respiratory ailments such as asthma.

He said bees would not come in contact with the spray because most spraying is done at dusk when bees are not out. And the spray wouldn’t hurt dogs or cats because the same ingredients in this insecticide are in flea collars and flea and tick dips used to keep insects off dogs and cats.